The invention relates to an insulated glazing unit (IGU) and its manufacture and, more particularly, to an IGU which includes an electronic physical shutter device that controls the intensity of radiation passing through the insulated glazing unit and/or that can block the radiation passing through the insulated glazing unit.
Glass windows, skylights, doors, and the like which are used in buildings and other structures are known to waste large amounts of energy. The windows permit the infrared radiation of sunlight to pass into the interior of the building and cause unwanted heating, particularly during summer months, thus requiring increased use of air conditioning to remove the unwanted heat. The windows also permit heat to leave the interior of the building during winter months, thereby requiring additional heating of the building. The increased use of air conditioning and heating increases the costs of operating the building and causes increased consumption of petroleum products and other non-recoverable resources. The increased consumption of these resources has become particularly critical as, for example, supplies of petroleum decrease and the price of petroleum rises. Also, at the same time that this increased consumption has become critical, new constructions of residential and commercial structures incorporate more glass than was used in older constructions, thereby further increasing consumption of these non-recoverable resources.
A known method of attempting to reduce the passage of radiation through a window is to use low emissivity glass, tinted or non-tinted, commonly known as Low E glass, which typically incorporates one or more metal based coatings. During winter months, the Low E glass reduces heat loss from the building through the windows by reflecting heat back into the interior of the building. During summer months, the Low E glass reduces interior heating of the building by preventing solar radiation from passing through the windows into the building and also reduces potential damage from the solar radiation. Tinted coatings are frequently added to the Low E glass to enhance its effectiveness. Unfortunately, the use of tinted Low E glass also requires a significant and undesirable trade-off between its optical clarity and its effectiveness in reducing the passage of heat and radiation through the tinted Low E glass. Specifically, the Low E glass requires thicker coatings to more effectively conserve energy, and such thicker coatings cause less light to pass through the window.
Another known approach uses an insulated glass (IG) window that incorporates one or more functional electronic layers between the two or more sheets of glass of the IG window. The electronic layers are somewhat clear in the absence of an applied voltage and allow heat and radiation to pass. When the voltage is applied, the electronic layers darken to reduce the passage of the heat and radiation. The materials used, such as liquid crystal layers, electrophoretic layers, and/or electrochromic layers, are also used in display devices. The electrochromic layers are the materials most commonly used for such electronic layers. An example of this approach is described in U.S. Pat. No. 6,972,888, titled “Electrochromic Windows and Method of Making the Same” and issued Dec. 6, 2005 to Poll, et al., the disclosure of which is incorporated herein by reference.
Undesirably, IG windows that incorporate functional electronic layers are difficult and costly to manufacture, have a questionable operating life, have undesirable operating temperatures, have very slow response times, provide incomplete darkening, and increase power consumption by their operation.
It is therefore desirable to reduce the passage of heat and radiation through a window or the like in a manner that avoids the tradeoffs and drawbacks of the above known approaches. It is further desirable to provide a manufacturing process for such windows that can be used by traditional manufacturers of window glass, thereby adding another economic advantage to the manufacture of such windows.